Peripherals and clock source

[GOAA]

Hello,

I am using the nrf52832 and would like to know the clock sources used by the external peripherals. From the searches, I found that PCLK16M is used for most of the peripherals but doesn't that mean the HFCLK will be on as long as the clocks are enabled.

What is the clock source used by GPIO and GPIOTE and other such peripherals? What's the clock source used for flash write and RAM operations?

Is there any site where I can refer what clock source is used by what peripheral?

Thanks in advance

[Mehmet Nuri]

its your choice actually. If you chose to have "high accuracy" interrupts(not work in sleep modes), it will use high frequency xtal. But you can initiate internal 32.768 kHz and have sleep mode enabled interrupts. Depends on your application.

[Håkon Alseth]

Hi,

 

What is the clock source used by GPIO and GPIOTE and other such peripherals? What's the clock source used for flash write and RAM operations?

The clock source for most* peripherals is always PCLK16M. This clock tree is sourced by the HFCLK, which can be HFXO (external 32M crystal) or HFINT (64 MHz internal RC oscillator).

* some are sourced by the LFCLK, like the RTC peripheral. Same principle applies there; you choose which source for the LFCLK (internal RC, external 32k, or synthesized from HFCLK).

R/W to both RAM and Flash is performed on the CPU speed, ie. 64MHz.

  

Is there any site where I can refer what clock source is used by what peripheral?

No, unfortunately not. All peripherals that are asynchronous, like UART without hardware flow control, will keep the HFCLK active in sleep.

 

Kind regards,

Håkon

[GOAA]

Thanks for your answer,

Håkon Alseth said:

his clock tree is sourced by the HFCLK, which can be HFXO (external 32M crystal) or HFINT (64 MHz internal RC oscillator)

I have a softdevice and I am not enabling HFXO nor HFINT anywhere. So, it will be by default HFCLK and whenever radio is ON, HFXO will be used right?

[Håkon Alseth]

Hi,

 

GOAA said:

I have a softdevice and I am not enabling HFXO nor HFINT anywhere. So, it will be by default HFCLK and whenever radio is ON, HFXO will be used right?

You are correct. The HFXO will then be started only on-demand by the softdevice, and after its done; you will go back to using HFINT.

 

Cheers,

Håkon

[jcondon]

This information belongs in the Product Specification document. A proper clock tree diagram is an important part of MCU documentation.